Field of the Invention
The present invention relates to a method and apparatus for feeding strip stock into a machine, such as a metal stamping press or the like, and is especially concerned with a roll type stock feeder.
The feeding of strip stock into machines, such as metal stamping presses, is well known and is often carried out by actuating the feed mechanism by the moving parts of the machine, such as a press.
In a press, for example, there is a reciprocating press slide which carries out the work to be done on the stock in the press, and during movement of the press slide, according to the prior art practices, mechanical feeding mechanisms are actuated as through a series of links, shafts, or belts and pulleys from the press crankshaft which drives the slide to feed stock into the press while synchronizing the feeding of the stock with the reciprocating motion of the press slide.
The amount of feed on each cycle can be changed in an arrangement of this nature, for example, by changing the diameter of a feed roll which frictionally engages the strip stock and effects the feeding of the stock into the press. The mechanical linkage, if employed, can also be adjusted to change the amount of rotation of the feed rolls, or changes can be made in a geared drive to the rolls if such a geared drive is provided. Frequently such mechanical feed systems employ a rotating cam mechanically driven by the press crankshaft which operates a lever to mechanically lift the pinch roll (the non-driven roll) off the stock. If any timing adjustment is to be made on such a mechanism, it becomes a mechanical adjustment that is approached with wrenches and possibly even changes of cams in order to alter the timing of opening and closing of the pinch roll. Some roll lift controls for use in extremely low speed electric feeds have also been employed where the speed of feeding is in the neighborhood of 40 cycles per minute and under as compared to speeds of up to 1500 strokes per minute when employing the principles of the present invention. Many of these prior art electrical feeds are built independent of the press standing on the floor in their own cabinet and not physically connected to the press. They use compressed air in cylinders or air bags to produce the force to open the rolls. Some such systems employ a solenoid valve to control the air to the pneumatic actuators that lift the pinch roll. The solenoid valve is in turn controlled by electrical contacts on the press limit switch that is driven in synchronism with the press crank shaft. In these systems it is possible to mechanically adjust the angular position of these contacts to produce opening and closing of the pinch roll at the desired position in the press cycle, but again, this is a mechanical adjustment carried out on the limit switch on the press itself in order to adjust timing of the feed. All of the expedients referred to above require time and/or extra parts to be provided for adjustment of the feed system and, in general, are troublesome, expensive, and time consuming.
In roll type feeders, the rolls are generally moved toward each other to engage the stock during a feed cycle and are separated from each other at the end of a feed cycle in order to leave the stock free during the working operation.
The operation of opening and closing the feed rolls in a roll type stock feeder is also important because of the time consumed in moving the rolls and for the reason that the closing force exerted on the rolls must produce sufficient frictional engagement of the rolls with the stock to effect feeding thereof when the rolls rotate but without damaging the stock when the rolls move together.
With the foregoing in mind, a primary objective of the present invention is the provision of a stock feeding arrangement, especially a roll type stock feeding arrangement, and a method of operation thereof, which produces superior results in connection with stock feeding.
Another object is the provision of a method and apparatus as referred to above in which the timing of the feed cycle may be easily adjusted, thereby leaving the maximum portion of the press cycle for feeding the stock as permitted by the particular requirements of the die being operated in the press, and thus, permitting maximum speed of operation of the machine with which the stock feeding apparatus is associated.